Device and method for qualitative and quantitative analysis of heavy metals utilizing rotary disc system

ABSTRACT

The present invention relates to a device and a method for qualitative and quantitative analysis of heavy metals and more particularly provides a device and a method for qualitative and quantitative analysis of heavy metals utilizing a rotary disc system.

BACKGROUND OF THE INVENTION Cross-Reference to Related Applications

This application is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/KR2018/012724, filed on Oct. 25, 2018, which claims priority to Korean Patent Application No. 10-2017-0154395, filed on Nov. 20, 2017, and Korean Patent Application No. 10-2018-0053636, filed on May 10, 2018, the disclosures of all of which are hereby incorporated herein by reference.

1. Field of the Invention

The present invention relates to a device and a method for qualitative analysis and quantitative analysis of heavy metals and, more particularly, to a device and a method for qualitative analysis and quantitative analysis of heavy metals using a rotatable disk system.

2. Description of the Related Art

In general, the most widely used method for detecting heavy metals is spectroscopic analysis such as inductively coupled plasma mass spectrometry or atomic absorption/emission spectrometry. Mass spectrometry and spectroscopy based heavy metal detection methods are accurate and have high detection limits, but they are expensive and require skilled analytical techniques, making it difficult to perform a heavy metal analysis in the field quickly and simply.

It is required to develop economical and cost-effective color development based heavy metal analysis system for replacing expensive mass spectrometry and spectroscopy based heavy metal analysis equipment, and development of miniaturized analysis system that can be conveniently applied in the field is required. In addition, it is required to develop a system capable of quantitative analysis as well as qualitative analysis of heavy metals while shortening analysis time by performing simultaneous detection of multiple heavy metals.

In addition, it is required to facilitate the qualitative/quantitative analysis of heavy metals with the naked eyes by making the color development reaction between the organic ligand coated on a detection unit and the heavy metal uniformly over the detection unit via more uniform movement of a fluid sample when the fluid sample is developed in the detection unit and by preventing the moisture condensation phenomenon in the detection unit. In addition, it is necessary to increase the detection limit by making the color developed distance longer so that the naked eyes can be identified by ensuring the color developed distance beyond a certain level even at a low heavy metal concentration.

SUMMARY OF THE INVENTION

The present invention pertains to a device for qualitative analysis and quantitative analysis comprising a rotatable platform and a plurality of microfluidic structures disposed radially and symmetrically on the rotatable platform. Each of the plurality of the microfluidic structures comprises a top layer comprising a sample injection unit into which a fluid sample containing heavy metals is injected and a microfluidic channel (a siphon channel) which is a passage through which the sample can be moved to a first detection unit and connects the sample injection unit to the one end of the first detection unit; the first detection unit coated with an organic substance capable of causing the color development reaction with heavy metals of the sample; and a bottom layer including a portion where the first detection unit is inserted and a ruler for measuring the color developed distance. Each of the plurality of the microfluidic structures may receive different kinds of samples. The rotation of the device is controlled so that the sample moves from the sample injection unit to the microfluidic channel and then to the first detection unit, and the qualitative analysis through the color development reaction of the heavy metals in the first detection unit and the quantitative analysis through the measurement of the color developed distance may be possible.

Further, the device for qualitative analysis and quantitative analysis according to the present invention further comprises an air circulation channel connecting between the sample injection unit and the other end of the first detection unit, wherein the air circulation channel can increase the rate of evaporation of the fluid sample in the first detection unit and prevent moisture condensation phenomenon in the first detection unit.

Further, the device for qualitative analysis and quantitative analysis according to the present invention comprises a reservoir area connecting the microfluidic channel with the first detection unit, wherein one end of the first detection unit can be accommodated in the reserve area.

Further, the device for qualitative analysis and quantitative analysis according to the present invention may comprise a second detecting unit having a width smaller than the width of the first detecting unit instead of the first detecting unit.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, the sample injection unit may include a space capable of receiving the sample and an opening through which the sample can be injected.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, the control of the rotation of the device can be accomplished by rotating the device firstly and then stopping so that the sample injected into the sample injection unit is moved to the microfluidic channel; rotating the device secondarily so that the sample moved to the microfluidic channel is moved to the reservoir area; and stopping the device so that sample moved to the reservoir area is developed in the first detection unit.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, one end of the sample injection unit and the detection unit are connected to the microfluidic channel and the microfluidic channel may include a portion of a “U” shaped tube so that the sample can be received within the microfluidic channel after the first rotation and before the second rotation of the device.

Also, in the device for qualitative analysis and quantitative analysis according to the present invention, the first rotation may be performed at 2000 to less than 4000 RPM for 5 to 20 seconds and the second rotation may be performed at 4000 to 6000 RPM for 3 to 10 seconds.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, the rotatable platform is a circular disk and may have a diameter of 12 cm to 20 cm.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, the heavy metals that may be included in the sample may comprise Fe²⁺, Zn²⁺, Hg²⁺, Cr⁶⁺, Ni²⁺, or Cu²⁺.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, the organic material previously applied to the first detection unit may comprise dimethylglyoxime, bathophenanthroline, dithiooxamide, dithizone, diphenylcarbazide, or 1-(2-pyridylazo)-2-naphthol.

Further, the present invention pertains to an analytic method of a fluid sample containing heavy metals by using the qualitative analysis and quantitative analysis device according to the present invention. The analytic method comprises: (S1) injecting the sample into the sample injection unit; (S2) controlling the rotation of the device; and (S3) performing at least one of qualitative analysis and quantitative analysis of the sample developed in the detection unit.

Further, in the analytic method of a fluid sample containing heavy metals according to the present invention, the injection of the sample into the sample injection unit of the step (S1) may comprise injecting the fluid sample containing different kinds of heavy metals into each of the plurality of microfluidic structures, or injecting the fluid sample containing same kinds of the heavy metals of varying concentrations into each of the plurality of microfluidic structures.

Further, in the analytic method of a fluid sample containing heavy metals according to the present invention, the controlling of the rotation of the device of the step (S2) may comprise (S2-1) rotating the device firstly and then stopping so that the sample injected into the sample injection unit is moved to the microfluidic channel; (S2-2) rotating the device secondarily so that the sample moved to the microfluidic channel is moved to the reservoir area; and (S2-3) stopping the rotation of the device so that the sample moved to the reservoir area is developed in the detection unit.

Further, in the analytic method of a fluid sample containing heavy metals according to the present invention, the performance of at least one of qualitative analysis and quantitative analysis of the sample of the step (S3) may comprise performing at least one of (S3-1) qualitative analysis through the color development reaction of the sample developed in the detection unit and (S3-2) the quantitative analysis through the measurement of the color developed distance.

Effect of the Invention

According to the device for qualitative analysis and quantitative analysis (1, 1′) and the analysis method of the sample using the same (2) according to one embodiment of the present invention, the increase of the detection limit of heavy metals through the control of the automated fluidic control and the control of the torque and capillary force is possible. It is possible to improve the detection limit of heavy metal ions by the torque control. That is, it is possible to improve the detection limit by controlling the color development reaction time and the colored area via adjustment of the centrifugal force and the capillary force by control of the rotation of the device.

According to the device for qualitative analysis and quantitative analysis (1, 1′) and the analysis method of the sample using the same (2) according to one embodiment of the present invention, qualitative analysis and quantitative analysis of several heavy metals can be performed with one device (1, 1′). According to the present invention, economical and rapid multi-metal qualitative/quantitative analysis is possible. It is more economical than conventional expensive spectroscopy or mass spectrometry based heavy metal detector and can shorten analysis time. In addition, the configurations for qualitative analysis and quantitative analysis can be integrated into one miniaturized device (1, 1′), and can be applied quickly and conveniently in the field where qualitative/quantitative analysis of heavy metals is required.

In addition, since the channel (a microfluidic channel) and the detection unit are all patterned in one device, the fabrication of the device for qualitative analysis and quantitative analysis (1, 1′) is simple.

Further, according to the device for qualitative analysis and quantitative analysis (1, 1′) and the analysis method of the sample using the same (2) according to one embodiment of the present invention, by providing an air circulation channel, it is possible to prevent the moisture condensation phenomenon in the detection unit when the fluid sample is developed in the detection unit, thereby making it easy to identify the color with the naked eyes and minimizing errors in analysis. Further, by providing a reservoir area at the end of the microfluidic channel and positioning one end of the detection unit within the reservoir area, the fluid sample moves more uniformly when the fluid sample is developed in the detection unit and the color development reaction between the organic ligand coated on the detection unit and the heavy metals of the sample can be made more uniform.

Further, by narrowing the width of the detection unit, the color developed distance becomes longer and the detection limit can be increased. That is, since the naked eye can be identified by ensuring the color developed distance beyond a certain level even at a low heavy metal concentration, by making the color developed distance longer, the sample can be detected even when the concentration of the heavy metal is lower.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a device for qualitative analysis and quantitative analysis according to one embodiment of the present invention, and FIGS. 1B and 1C show microfluidic structures of the device for qualitative analysis and quantitative analysis of FIG. 1A.

FIG. 2A illustrates a device for qualitative analysis and quantitative analysis according to another embodiment of the present invention, and FIGS. 2B and 2C show microfluidic structures of the device for qualitative analysis and quantitative analysis of FIG. 2A.

FIGS. 3A to 3D show each layer of a rotatable platform comprising microfluidic structures.

FIG. 4 shows an example of a color development reaction between heavy metals ions and organic complexing agents.

FIG. 5 shows an example of simultaneous qualitative analysis of heavy metals using the device for qualitative analysis and quantitative analysis according to the present invention.

FIGS. 6A and 6B show examples of quantitative analysis of heavy metals using the device for qualitative analysis and quantitative analysis according to the present invention.

FIG. 7 shows the results of the development of the sample at each detector of the devices for qualitative analysis and quantitative analysis of FIGS. 1A and 2A.

FIG. 8 shows a flowchart of a method of analyzing a sample using the device for qualitative analysis and quantitative analysis according to the present invention.

FIG. 9 shows a system for qualitative analysis and quantitative analysis that includes and can rotate the device for qualitative analysis and quantitative analysis according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the device for qualitative analysis and quantitative analysis comprising a rotatable platform and a plurality of microfluidic structures disposed radially and symmetrically on the rotatable platform according to present invention, each of the plurality of microfluidic structures comprises a top layer comprising a sample injection unit into which a fluid sample containing heavy metals is injected and a microfluidic channel which is a passage through which the sample can be moved to a first detection unit and connects the sample injection unit to the one end of the first detection unit; the first detection unit coated with an organic substance capable of causing the color development reaction with heavy metals of the sample; and a bottom layer including a portion where the first detection unit is inserted and a ruler for measuring the color developed distance. Each of the plurality of the microfluidic structures may receive different kinds of samples. The rotation of the device is controlled so that the sample moves from the sample injection unit to the microfluidic channel and then to the first detection unit, and the qualitative analysis through the color development reaction of the heavy metals in the first detection unit and the quantitative analysis through the measurement of the color developed distance may be possible.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, it further may comprise an air circulation channel connecting between the sample injection unit and the other end of the first detection unit, wherein the air circulation channel can increase the rate of evaporation of the fluid sample in the first detection unit and prevent moisture condensation phenomenon in the first detection unit.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, it may comprise a reservoir area connecting the microfluidic channel with the first detection unit, wherein one end of the first detection unit may be accommodated in the reserve area.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, it may comprise a second detecting unit having a width smaller than the width of the first detection unit instead of the first detection unit.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, the sample injection unit may include a space capable of receiving the sample and an opening through which the sample can be injected.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, the control of the rotation of the device can be accomplished by rotating the device firstly and then stopping so that the sample injected into the sample injection unit is moved to the microfluidic channel; rotating the device secondarily so that the sample moved to the microfluidic channel is moved to the reservoir area; and stopping the device so that sample moved to the reservoir area is developed in the first detection unit.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, one end of the sample injection unit and the detection unit are connected to the microfluidic channel and the microfluidic channel may include a portion of a “U” shaped tube so that the sample may be received within the microfluidic channel after the first rotation and before the second rotation of the device.

Also, in the device for qualitative analysis and quantitative analysis according to the present invention, the first rotation may be performed at 3000 RPM for 10 seconds, the second rotation may be performed at 5000 RPM for 5 seconds.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, the rotatable platform is a circular disk and may have a diameter of 12 cm to 20 cm.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, the heavy metals that may be included in the sample may be Fe²⁺, Zn²⁺, Hg²⁺, Cr²⁺, Ni²⁺, or Cu²⁺.

Further, in the device for qualitative analysis and quantitative analysis according to the present invention, the organic material previously applied to the first detection unit may comprise dimethylglyoxime, bathophenanthroline, dithiooxamide, dithizone, diphenylcarbazide, or 1-(2-pyridylazo)-2-naphthol.

Further, in the analytic method of a fluid sample containing heavy metals by using the qualitative analysis and quantitative analysis device according to the present invention, the method comprises: (S1) injecting the sample into the sample injection unit; (S2) controlling the rotation of the device; and (S3) performing at least one of qualitative analysis and quantitative analysis of the sample developed in the detection unit.

Further, in the analytic method of a fluid sample containing heavy metals according to the present invention, the injection of the sample into the sample injection unit of the step (S1) may comprise injecting fluid sample containing different kinds of the heavy metals into each of the plurality of microfluidic structures, or injecting fluid sample containing same kinds of heavy metals of varying concentrations into each of the plurality of microfluidic structures.

Further, in the analytic method of a fluid sample containing heavy metals according to the present invention, the controlling of the rotation of the device of the step (S2) may comprise (S2-1) rotating the device firstly and then stopping so that the sample injected into the sample injection unit is moved to the microfluidic channel; (S2-2) rotating the device secondarily so that the sample moved to the microfluidic channel is moved to the reservoir area; and (S2-3) stopping the rotation of the device so that the sample moved to the reservoir area is developed in the detection unit.

Further, in the analytic method of a fluid sample containing heavy metals according to the present invention, the performance of at least one of qualitative analysis and quantitative analysis of the sample of the step (S3) may comprise performing at least one of (S3-1) qualitative analysis through the color development reaction developed in the detection unit and (S3-2) the quantitative analysis through the measurement of the color developed distance.

Hereinafter, the device and the method for qualitative analysis and quantitative analysis of heavy metals using a rotatable disk system according to the present invention will be described in detail. The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the present invention and the technical scope of the present invention is not limited thereto.

In addition, the same or corresponding components are denoted by the same reference numbers regardless of the figures, and redundant description thereof will be omitted. For convenience of explanation, the size and shape of each constituent member shown may be exaggerated or reduced.

FIG. 1A shows a device for qualitative analysis and quantitative analysis (1) according to one embodiment of the present invention, and FIG. 1B shows microfluidic structures (20) of the rotatable disk system of FIG. 1A.

First, referring FIG. 1A, the device for qualitative analysis and quantitative analysis (1) includes the rotatable platform (10) and a plurality of the microfluidic structures (20) provided on the rotatable platform (10). The rotatable platform (10) may be, for example, a circular disk, and the size may be, for example, in one embodiment, 12 cm to 20 cm in diameter, and in another embodiment, less than 12 cm in diameter.

The rotatable platform (10) includes the plurality of microfluidic structures (20) which are positioned radially and symmetrically on the rotatable platform (10). For example, the plurality of microfluidic structures (20) may comprise two, four, six, eight, ten, or twelve of the structures. In FIG. 1A, six microfluidic structures (20) are shown disposed on the rotatable platform (10).

Referring to FIG. 1B, each microfluidic structure (20) of the plurality of microfluidic structures (20) is shown. The microfluidic structures (20) include a top layer (see FIG. 3B), a detection unit (120) coated with an organic substance capable of causing a color development reaction with the heavy metals in a fluid sample, and a bottom layer (see FIG. 3D). The top layer includes a sample injection unit (100) into which a fluid sample containing heavy metals is injected and a microfluidic channel (110) through which the fluid sample can move to the detection unit. The bottom layer includes a portion where the first detection unit (120) can be inserted (see FIG. 3D) and a ruler (130) for measuring the color developed distance.

Each microfluidic structure (20) of the plurality of the microfluidic structures (20) may receive the fluid sample containing different kinds of the heavy metals. The heavy metals that may be included in the fluid sample may include, for example, Fe²⁺, Zn²⁺, Hg²⁺, Cr⁶⁺, Ni²⁺, or Cu²⁺.

The sample injection unit (100) includes a space for accommodating a fluid sample containing the heavy metals and an opening (100 a) through which the fluid sample can be injected into the space. The sample injection unit (100) and one end of the first detection unit (120) may be connected to the microfluidic channel (110). Further, the sample injection unit (100) may include a blocking unit (100 b) which prevents the sample injected through the opening (100 a) from flowing directly into the microfluidic channel (110) and stores the sample in the inner space of the sample injection unit (100) by using drop of the channel. Since the vicinity of the rear end portion (100 c) of the sample injection unit (100) where the sample injection unit (100) and the microfluidic channel (110) are connected to each other in the sample injection unit (100) has, for example, a streamlined shape, when the fluid sample injected into the injection unit (100) moves to the microfluidic channel (110), the resistance of the fluid sample is minimized and all of the fluid sample injected into the sample injection unit (100) is moved to the microfluidic channel (110).

The microfluidic channel (110) may have a width of 1 mm and a depth of 100 μm. The microfluidic channel (110) may comprise, for example, a portion of a “U” shaped tube. As will be described below, the fluid sample including heavy metals after the first rotation and before the second rotation of the device for qualitative analysis and quantitative analysis (1) has the passage through which the fluid sample moves due to the hydrophilicity of the microfluidic channel (110), and as a result, the fluid sample can be accommodated in the microfluidic channel (110).

The first detection unit (120) may be coated with an organic material capable of causing a color development reaction with heavy metals of the fluid sample so that the fluid sample can be developed. The first detection unit (120) may be made of a porous hydrophilic material, for example, paper, nitrocellulose, cotton, silica based sol-gel matrix, etc., and may be preferably made of paper.

The ruler (130) is positioned alongside of the first detection unit (120) in the vicinity of the first detection unit (120). The ruler (130) may be, for example, scaled in millimeters (mm). Alternatively, it may be scaled in units of concentration such as ppm, ppb, etc., in addition to the length unit such as mm in the scale unit (130). In the case where the scale is expressed in terms of the concentration unit in the ruler (130), it may be expressed in terms of a concentration unit obtained by substituting the development distance of the heavy metals into a calibration curve (see FIGS. 6A and 6B).

The device for qualitative analysis and quantitative analysis (1) also includes an air circulation channel (140). The air circulation channel (140) connects between the sample injection unit (100) and the other end of the first detection unit (120). Due to this, the sample injection unit (100), the microfluidic channel (110), the first detection unit (120), the air circulation channel (140), and the sample injection unit (100) are connected to be circulated in order. By introducing the air circulation channel (140), the evaporation rate of the fluid sample of the first detection unit (120) is increased, and the moisture condensation phenomenon in the first detection unit (120) is prevented. On the other hand, with respect to the sample injection unit (100), since the air circulation channel (140) is located at the center of the circular disk-shaped rotatable platform (10) and the microfluidic channel (110) is positioned toward the edge of the rotatable platform (10), when the rotatable platform (10) rotates, the sample of the sample injection unit (100) moves to the microfluidic channel (110) by the centrifugal force and does not move to the air circulation channel (140). Additionally, in order to prevent the possibility of movement, a hole having a depth of about 1 mm and a diameter of about 0.8 mm is drilled at a point where the sample injection unit (100) and the air circulation channel (140) are connected to each other to form a capillary valve operated by an air pressure, thereby preventing the sample from moving from the sample injection unit (100) to the air circulating channel (140).

The device for qualitative analysis and quantitative analysis (1) further includes a reservoir area (150) at the location where the microfluidic channel (110) is connected to the first detection unit (120), and one end of the first detection unit (120) is accommodated in the reservoir area (150). The reservoir area (150) is a recessed patterned area in each of the top and bottom layers (see FIG. 3A) of the rotatable platform (10) so that the fluid sample can be received therein. The fluid sample accommodated in the microfluidic channel (110) during the first rotation of the rotatable platform (10) moves from the microfluidic channel (110) to the reservoir region (150) during the second rotation of the rotatable platform (10) and then is stored (I.e., trapped) in the reservoir area (150) without being developed into the first detection unit (120) by the centrifugal force due to the rotation. When the second rotation of the rotatable platform (10) is stopped, the fluid sample is developed into the first detection unit (120) connected to the reservoir area (150). A more detailed description thereof will be given below with reference to FIG. 8 .

One end of the first detection unit (120) is accommodated in the reservoir region (150), while the fluid sample is injected from the microfluidic channel (110) located in the top layer of the rotatable platform (10) to one end of the first detection unit (120′) inserted into the bottom layer of the rotatable platform (10), that is, downward. Therefore, the fluid sample can be developed more uniformly in the first detection unit (120).

FIG. 1C shows exemplary dimensions of the microfluidic structures (20) of the rotatable disk system of FIG. 1B. Exemplary dimensions of the microfluidic structures (20) are not limited to those shown in FIG. 1C, but may be modified or changed according to various environments embodied in the present invention.

FIG. 2A shows a device for qualitative analysis and quantitative analysis (1′) according to another embodiment of the present invention, and FIG. 2B shows the microfluidic structures (20′) of the rotatable disk system of FIG. 2A. The device for qualitative analysis and quantitative analysis (1′) of FIG. 2A, like the device for qualitative analysis and quantitative analysis (1) of FIG. 1A, comprises the rotatable platform (10) and a plurality of the microfluidic structures (20′) provided in and the rotatable platform (10). The top layer of the rotatable platform (10) includes the sample injection unit (100) into which a fluid sample containing heavy metals is injected and the microfluidic channel (110) which is a passage through which the fluid sample can move to the detection unit. The bottom layer includes a portion where the detection unit (120′) can be inserted (see FIG. 3D) and the ruler (130) for measuring the color developed distance.

In FIGS. 2A and 2B, the width of the second detection unit (120′) is smaller than the width of the first detection unit (120) in FIGS. 1A and 1B. Accordingly, in the second detection unit (120′), the color developed distance is longer than that of the first detection unit (120), and thus the detection limit increases. In this connection, reference is made to the experimental results shown in FIG. 7 . FIG. 7 shows the experimental results regarding the color developed distance, wherein when the width of the second detection unit (120′) is reduced to 50% of the first detection unit (120) (for example, when the length of the first detection unit (120) is 60 mm and the width is 5 mm, and when the second detection unit (120′) has a length of 60 mm and a width of 2.5 mm), the concentration of each heavy metal in the sample is 100 ppm.

For example, when the width of the second detection unit (120′) is 50% smaller than the width of the first detection unit (120), the color developed length can be increased by about 20 to 50% and the detection limit can be doubled.

FIG. 2C illustrates exemplary dimensions of the microfluidic structures (20) of the rotatable disk system of FIG. 2B.

In the description of the device for qualitative analysis and quantitative analysis (1′) of FIG. 2A and the microfluidic structures (20′) of FIG. 2B, the description of the components that overlap with those in the device for qualitative analysis and quantitative analysis (1) of FIG. 1A and the microfluidic structures (20) of FIG. 1B refers to the descriptions of FIGS. 1A and 1B.

FIGS. 3A to 3D illustrate each layer of the rotatable platform (10) comprising the microfluidic structures (20) of FIG. 1A. As shown in FIG. 3A, the rotatable platform (10) including the microfluidic structures (20) is mainly composed of three layers, each of which corresponds to the top layer wherein the sample injection unit (100) and the microfluidic channel (110) are positioned (see FIG. 3B), a bottom layer (see FIG. 3D) for inserting the detection unit, and a PSA (Pressure sensitive adhesion) layer (see FIG. 3C) for bonding the top and bottom layers. The materials of the top and bottom layers may include, for example, polycarbonate (PC), polymethyl methacrylate (PMMA) and the like. The sample injection unit (100) and the microfluidic channel (110) are provided within the top layer, and the sample injection unit (100) and the microfluidic channel (110) can be formed through a patterning process using micro-milling. The lower surface of the top layer where the first and second detection units (120, 120′) are positioned may be variously modified and changed so that the first and second detection units (120, 120′) can be inserted, including a concave portion in conformity with the shape of the first and second detection units (120, 120′). Also, the depth of the concave portion can be variously modified and changed according to the environment in which the present invention is actually implemented. A hydrophilic material is coated on the inside of the microfluidic channel (110) to receive the fluid sample containing the heavy metals. A space in which the first and second detection units (120, 120′) can be inserted is provided and the ruler (130) is patterned in the bottom layer. Since the space in which the first and second detection units (120, 120′) can be inserted is provided in the bottom layer, the fluid sample is supplied from the sample injection unit (100) and the microfluidic channel (110) provided in the top layer to the first and second detection units (120, 120′). Since the fluid sample flows downward to the first and second detection units (120, 120′), the fluid sample is more uniformly developed from the one end of the first and second detection units (120, 120′) than in the case where the microfluidic channel (110) and the first and second detection units (120, 120′) are positioned in the same layer. The PSA layer is an adhesive layer serving to bond the top layer and the bottom layer, and can be formed into, for example, an acryl based double-sided adhesive tape. In a tape or a plate having an adhesive component corresponding to the size of the rotatable platform (10), the region corresponding to the sample injection unit (100) and the microfluidic channel (110) in the top layer, and the region corresponding to the first and second detection units (120, 120′) in the bottom layer may be removed by cutting or the like, as shown in FIG. 3C. On the other hand, the top layer and the PSA layer are made of a transparent material so that the development of the sample in the detection unit (120) and the ruler (130) in the bottom layer can be identified. However, the present invention is not limited to the above-described embodiments, and various modifications and changes are possible, for example, the ruler (130) may be patterned on the top layer.

According to the device for qualitative analysis and quantitative analysis (1, 1′) of the present invention, the rotation of the device for qualitative analysis and quantitative analysis (1) is controlled so that the fluid sample containing the heavy metals moves from the sample injecting unit (100) into the microfluidic channel (110), and then moves to the first and second detection units (120, 120′). For example, after the fluid sample containing heavy metals is injected into the sample injection unit (100), when the device for qualitative analysis and quantitative analysis (1, 1′) is first rotated for 10 seconds at 3000 RPM and then stopped, the fluid sample containing the heavy metals moves to the microfluidic channel (110). When the device for qualitative analysis and quantitative analysis (1, 1′) is secondarily rotated at 5,000 RPM for 5 seconds, the fluid sample containing the heavy metals in the microfluidic channel (110) of the top layer is injected to the reservoir area (150) inserted in the bottom layer by the centrifugal force. When the rotation of the device for qualitative analysis and quantitative analysis (1, 1′) is stopped, the fluid sample containing heavy metals is developed on the first and second detection units (120, 120′) by the capillary force.

The fluid sample including the heavy metals developed on the detection unit (120, 120′) reacts with the reagents previously coated on the detection unit (120, 120′) to indicate colors related to the heavy metals. As an organic substance that can be previously applied to the detection unit (120, 120′), for example, an organic chelating agent may be used. In one embodiment, organic substances based on a reaction list between heavy metal ions and the organic chelating agents as shown in Table 1 below may be used.

TABLE 1 Heavy Metals Form Chelating agent (concentration) Nickel (Ni²⁺) Sulfate Dimethylglyoxime (100 mM) Iron (Fe²⁺) Sulfate Bathophenanthroline (5 mM) Copper (Cu²⁺) Sulfate Dithiooxamide (20 mM) Mercury (Hg²⁺) Sulfate Dithizone (5 mM) Chromium (Cr⁶⁺) Oxide Diphenylcarbazide (10 mM) Zinc (Zn²⁺) Sulfate 1-(2-Pyridylazo)-2-naphthol (5 mM)

FIG. 4 shows the color development reaction between heavy metal ions and the organic chelating agents according to Table 1. In the embodiment of FIG. 4 , PAN (1-(2-pyridylazo)-2-naphthol), Bphen (bathophenanthroline), DMG (dimethylglyoxime), DTO (dithiooxamide), DCB (diphenylcarbazide) and DTZ (dithizone) were used as the organic chelating agents. And 1% H₂SO₄ was added to DCB for Cr⁶⁺ to improve the reaction selectivity of Cr⁶⁺ ion for DCB and the color development reaction.

The device for qualitative analysis and quantitative analysis (1, 1′) according to the present invention can provide a simultaneous qualitative analysis up to a level of 25 ppm for a plurality of heavy metals such as Fe²⁺, Zn²⁺, Hg²⁺, Cr⁶⁺, Ni²⁺, or Cu²⁺ within 15 minutes.

FIG. 5 shows an example of a simultaneous qualitative analysis for six heavy metals (100 ppm) using the device for qualitative analysis and quantitative analysis (1) of FIG. 1A. The qualitative analysis can be performed on the heavy metals contained in the fluid sample with the hue according to the color development reaction on the first and second detection unit (120, 120′). For example, when the hue according to the color development reaction of the fluid sample is observed with the naked eyes, it is possible to identify the kind of the heavy metals contained in the sample.

In addition, the degree of development of the fluid sample including the heavy metals on the first and second detection unit (120, 120′) can be quantitatively analyzed by using the ruler (130). Referring to the example of FIG. 5 , it can be seen that the degree of development of the fluid sample including heavy metals on the detection unit (120′) of each of the plurality of microfluidic structures (20) is different from each other. It is possible to measure the extent to which a fluid sample containing the heavy metals is developed by using the ruler (130). The development distance of the corresponding fluid sample on the detection unit (120) is measured using the respective ruler (130), the types of heavy metals contained in the fluid sample are determined by the above qualitative analysis, and the quantitative analysis of the heavy metals can be performed by substituting the development distance into a calibration curve for the heavy metals (see FIGS. 6A and 6B). As one example of quantitative analysis, FIG. 6A shows a case where Cr⁶⁺ is quantitatively analyzed and FIG. 6B shows a case where Fe²⁺ is quantitatively analyzed using the device for qualitative analysis and quantitative analysis (1) of FIG. 1A. For example, the numbers of 1 ppm, 5 ppm, 10 ppm, 25 ppm, 50 ppm, and 100 ppm described in FIG. 6A are the results of quantitative analysis of Cr⁶⁺. This is a method in which the degree of purple development corresponding to Cr⁶⁺ on the six detection units (120) is measured using the ruler (130) and then the measured development distance is substituted into the calibration curve of Cr⁶⁺ to obtain the concentration on the x axis corresponding to the degree of development on the y axis of the calibration curve so as that the quantitative analysis of Cr⁶⁺ can be performed. In the case of Fe²⁺ in FIG. 6B, the quantitative analysis can be performed in the same manner. At this time, in the case of Cr⁶⁺, the detection limit of the qualitative analysis is 1 ppm and the detection limit of the quantitative analysis is 5 ppm. In the case of Fe²⁺, the detection limit of the qualitative analysis is 25 ppm and the detection limit of the quantitative analysis is 50 ppm.

Hereinafter, with reference to FIG. 8 , a method (2) of analyzing a fluid sample containing the heavy metals using the device for qualitative analysis and quantitative analysis (1, 1′) according to one embodiment of the present invention will be described. The steps of the method for analyzing a sample (2) according to an embodiment of the present invention are as follows:

Step 1: Injecting a fluid sample into the sample injection unit (100) of the device for qualitative analysis and quantitative analysis (1, 1′) (S1);

Step 2: Controlling the rotation of the device for qualitative analysis and quantitative analysis (1, 1′) (S2); and

Step 3: Performing at least one of qualitative analysis and quantitative analysis (S3).

Step 1: Injecting a Fluid Sample into the Sample Injection Unit (100) of the Device for Qualitative Analysis and Quantitative Analysis (1, 1′) (S1)

The fluid sample is injected into each sample injection unit (100) of the plurality of the microfluidic structures (20) of the device for qualitative analysis and quantitative analysis (1, 1′). For example, about 40 μl of the fluid sample each can be injected into each sample injection unit (100). However, the present invention is not limited to this embodiment, and the amount of the injection can be variously adjusted according to various environments in which the present invention is implemented. The fluid sample containing different kinds of the heavy metals is respectively injected into each of the plurality of the microfluidic structures (20, 20′) (S1-1) to perform qualitative analysis and/or quantitative analysis as described below, the fluid sample containing the same kind of the heavy metals of varying concentrations are respectively injected into each of the microfluidic structures (20, 20′) (S1-2) to perform qualitative analysis and/or quantitative analysis as described below.

Step 2: Controlling the Rotation of the Device for Qualitative Analysis and Quantitative Analysis (1, 1′) (S2)

The device for qualitative analysis and quantitative analysis (1, 1′) is mounted on a system for qualitative analysis and quantitative analysis (3) capable of rotating the device for qualitative analysis and quantitative analysis (1, 1′), for example, a rotatable system for qualitative analysis and quantitative analysis (3) as shown in FIG. 9 , and the device for qualitative analysis and quantitative analysis (1, 1′) is rotated. This step (S2) includes the following detailed steps:

Step 2-1: The device for qualitative analysis and quantitative analysis (1, 1′) is initially rotated at 2000 to less than 4000 RPM for 5 to 20 seconds and then is stopped to move the fluid sample including heavy metals injected into the sample injection unit (100) located at the top layer of the microfluidic structure (20, 20′) to the microfluidic channel (110) (S2-1).

Step 2-2: The device for qualitative analysis and quantitative analysis (1, 1′) is secondarily rotated at 4000 to 6000 RPM for 3 to 10 seconds to flow the fluid sample including heavy metals transferred to the microfluidic channel (110) at step 2-1 into the reservoir region (150) of the microfluidic structures (20, 20′) (S2-2).

Step 2-3: The rotation of the device for qualitative analysis and quantitative analysis (1, 1′) is stopped so that the fluid sample including the heavy metals are guided by the capillary force from the reservoir region (150) to one end of the detection unit (120, 120′) accommodated in the reservoir region (150) to be developed on the detection unit (120, 120′) (S2-3).

Step 3: Performing at Least One of Qualitative Analysis and Quantitative Analysis (S3)

A qualitative analysis can be performed on the fluid sample developed on the detection unit (120, 120′) by a method of analyzing the color development reaction on the detection unit (120, 120′) with the naked eyes (S3-1), or a quantitative analysis can be performed by measuring the degree of development of the fluid sample developed on the detection unit (120, 120′) by using a ruler (130) and then substituting the measured values to the calibration curves of the corresponding heavy metals developed on the scale (S3-2), or both of the quantitative analysis and the quantitative analysis can be performed (S3-1 and S3-2). Examples related to this are described above with reference to FIGS. 5, 6A and 6B.

In summary, the device for qualitative analysis and quantitative analysis (1, 1′) according to an embodiment of the present invention includes the microfluidic structures (20) having the same structure that can detect a plurality of types (for example, six kinds) of heavy metals on a rotatable platform (10) (for example, a circular disk), wherein each microfluidic structure (20) is arranged radially and symmetrically along the rotational direction of the rotatable platform (10) and comprises the detection unit (120, 120′) coated with an organic substance that can cause a color development reaction with the heavy metals.

According to the device for qualitative analysis and quantitative analysis (1, 1′) and the method of analyzing the sample using the same (2) according to the embodiment of the present invention, the centrifugal force generated upon rotation of the device for qualitative analysis and quantitative analysis (1, 1′) can move the fluid sample containing the heavy metals to the detection unit (120, 120′) and the qualitative analysis can be performed through the color development reaction. Further, the fluid can be developed by the paper capillary force when the rotation of the device stops and the quantification may be performed by identifying the color developed distance with the ruler (130) patterned on the device for qualitative analysis and quantitative analysis (1, 1′). It is possible to increase the detection limit of heavy metals through automatic fluid control and control of torque and capillary force. It is possible to improve the detection limit of heavy metal ions by the torque control. That is, by adjusting the centrifugal force and the capillary force by the rotation control, it is possible to improve the detection limit by controlling the reaction time of color development and the colored area. Specifically, when the development speed of the sample containing heavy metals due to the capillary force becomes faster than the speed at which the heavy metals and the organic chelating agent react with each other on the detection unit, the sample containing the heavy metals fails to sufficiently react with the organic chelating agent and develops on the entire detection unit. In the case of a heavy metal sample having a high concentration, there is no problem in detection because of the color appears, but there is a possibility that the quantitative property is lowered. In the case of a heavy metal sample of low concentration, there is a possibility that the color development does not occur due to insufficient reaction with the organic chelating agent of the detection unit, and the detection sensitivity and limitations may be lowered. However, according to the present invention, since the centrifugal force acts on the opposite side of the capillary force, the centrifugal force is applied to control the solution development speed by the capillary force so that the color development reaction can be sufficiently performed on the detection unit to improve the detection limitations.

Further, according to the device for qualitative analysis and quantitative analysis (1, 1′) and the method of analyzing the sample using the same (2) according to the embodiment of the present invention, it is economical and quick in the qualitative/quantitative analysis of multiple heavy metals. It is more economical than conventional expensive spectroscopy or mass spectrometry based heavy metal detector and can shorten analysis time. Thus, it can be applied quickly and conveniently in the field where the qualitative/quantitative analysis of heavy metals is required.

The technical constitution of the present invention as described above will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. In addition, the scope of the present invention is indicated by the appended claims rather than the detailed description of the invention. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

EXPLANATION OF REFERENCE NUMBERS

-   -   1, 1′: Device for qualitative analysis and quantitative analysis     -   2: Method of analyzing a sample     -   3: System for qualitative analysis and quantitative analysis     -   10: Rotatable platform     -   20, 20′: Microfluidic structure     -   100: Sample injection unit     -   110: Microfluidic channel     -   120, 120′: Detection unit     -   130: Ruler     -   140: Air circulation channel     -   150: Reservoir area 

What is claimed is:
 1. A device for qualitative analysis and quantitative analysis comprising a rotatable platform and a plurality of microfluidic structures disposed radially and symmetrically on the rotatable platform, wherein each of the plurality of the microfluidic structures comprises: a top layer comprising a sample injection unit configured to receive an injection of a respective fluid sample containing heavy metals and a microfluidic siphon channel which is a passage providing fluid communication between the sample injection unit and one end of a first detection unit or a second detection unit; the first detection unit and the second detection unit each coated with an organic substance configured to produce a color development reaction with the heavy metals of the fluid sample; and a bottom layer including a portion into which the first detection unit or the second detection unit is inserted and a ruler configured to measure a color developed distance of the color development reaction, wherein each of the plurality of the microfluidic structures is configured to receive a different kind of the respective fluid samples than other ones of the plurality of the microfluidic structures, wherein the device is configured to move the respective fluid samples from the respective sample injection unit to the respective microfluidic channel and then to the respective first detection unit or the respective second detection unit when the rotatable platform is rotated, wherein the device is configured to provide a qualitative analysis of the fluid samples through the respective color development reaction of the heavy metals in the respective first detection unit or the respective second detection unit and the device is configured to provide a quantitative analysis of the fluid samples through measurement of the respective color developed distances, wherein one or more of a first subset of the microfluidic structures each has a respective one of the first detection units and one or more of a second subset of the microfluidic structures each has a respective one of the second detection units, each of the microfluidic structures that does not have one of the first detection units has a respective one of the second detection units, and each of the second detecting units has a width smaller than a width of each of the first detecting units, and wherein the device is configured to develop a same amount of each of the respective fluid samples only by capillary force without centrifugal force.
 2. The device according to claim 1, further comprising a respective air circulation channel connecting each sample injection unit and another end of each respective first detection unit, wherein each air circulation channel is configured to increase a rate of evaporation of the fluid sample in the respective first detection unit and is configured to prevent a moisture condensation phenomenon in the respective first detection unit.
 3. The device according to claim 1, further comprising a respective reservoir area connecting each microfluidic siphon channel with each respective first detection unit, wherein the one end of the respective first detection unit is accommodated in the respective reservoir area.
 4. The device according to claim 3, wherein the device is configured to move the respective fluid samples by: a first rotation of the rotatable platform and then stopping the first rotation so that the fluid sample injected into each respective sample injection unit is moved to the respective microfluidic channel; a second rotation of the rotatable platform so that the fluid sample moved to each respective microfluidic siphon channel is moved to the respective reservoir area; and stopping rotation of the rotatable platform so that the fluid sample moved to each respective reservoir area is developed in the first detection unit.
 5. The device according to claim 4, wherein each microfluidic siphon channel includes a portion of a “U” shaped tube that is configured to receive the respective fluid sample after the first rotation and before the second rotation of the rotatable platform.
 6. The device according to claim 4, wherein the first rotation of the rotatable platform is performed at 2000 to less than 4000 RPM for 5 to 20 seconds and the second rotation of the rotatable platform is performed at 4000 to 6000 RPM for 3 to 10 seconds.
 7. The device according to claim 1, wherein the rotatable platform is a circular disk having a diameter of 12 cm to 20 cm.
 8. The device according to claim 1, wherein the heavy metals included in each of the fluid samples comprise Fe²⁺, Zn²⁺, Hg²⁺, Cr⁶⁺, Ni²⁺, or Cu²⁺.
 9. The device according to claim 8, wherein the organic substance that coats the first detection units comprises dimethylglyoxime, bathophenanthroline, dithiooxamide, dithizone, diphenylcarbazide, or 1-(2-pyridylazo)-2-naphthol.
 10. A method of analyzing the fluid samples by using the device according to claim 1, the method comprising: injecting each fluid sample into the respective sample injection unit; rotating the rotatable platform; and performing at least one of the qualitative analysis and the quantitative analysis of the fluid sample developed in each respective detection unit.
 11. The method according to claim 10, wherein the injecting of each fluid sample into the respective sample injection unit comprises: injecting a first amount of each fluid sample into the respective one of the microfluidic structures; or injecting a second amount of each fluid sample into the respective one of the microfluidic structures, the first amount of each fluid sample having a different concentration than the second amount of each fluid sample.
 12. The method according to claim 10, wherein the performing of the at least one of the qualitative analysis and the quantitative analysis of each fluid sample comprises: performing the at least one of the qualitative analysis through the color development reaction of each sample developed in the respective detection unit and the quantitative analysis through the measurement of the respective color developed distance.
 13. A method of analyzing the fluid samples by using the device according to claim 3, the method comprising: injecting each fluid sample into the respective sample injection unit; rotating the rotatable platform; and performing at least one of the qualitative analysis and the quantitative analysis of the fluid sample developed in each respective detection unit, wherein the rotating of the rotatable platform comprises: rotating the rotatable platform firstly and then stopping the rotating so that the fluid sample injected into each respective sample injection unit is moved to the respective microfluidic channel; rotating the rotatable platform secondarily so that the fluid sample moved to each microfluidic channel is moved to the respective reservoir area; and stopping the rotation of the rotatable platform so that the sample moved to each reservoir area is developed in the respective detection unit. 